1. Field
The present invention relates to an apparatus for testing a tensile strength under a high temperature condition and a unit for measuring elongation provided in the same, and more particularly, to an apparatus for measuring a tensile strength and elongation of a test sample under a high temperature condition.
2. Description of the Related Art
In general, a fire generated in a closed concrete structure may cause serious damage to the concrete structure. In particular, a fire generated in an enclosure such as an underground space increases a temperature to 1000° C. or more within several minutes after the fire and then is maintained for a long time. In this case, a spalling failure may occur, causing damage to concrete, which is a construction material of the concrete structure.
The spalling failure means that, when a large amount of heat of 400° C. or more is continuously applied to the concrete, moisture confined in the concrete explosively bursts out, causing damage to the concrete surface and melting reinforcing bars in the concrete so that the structure easily collapses.
While it has been known that the concrete structure has material characteristics such as low thermal conductivity and a non-combustible property, the structural performance may abruptly decrease due to the spalling failure generated from the concrete surface under a high temperature exposure circumstance such as a fire.
When the spalling failure occurs, the reinforcing bars in the concrete are also exposed to a high temperature and directly affected by the heat. Therefore, in order to measure structural deformation of the reinforcing bars due to the fire, a test for measuring strain and elongation of the reinforcing bars under the high temperature condition is essential.
However, since a conventional tensile strength test apparatus and a conventional elongation measuring apparatus are configured without consideration of the high temperature condition, it is impossible to accurately measure variation in tensile strength, strain and elongation of a test sample such as a reinforcing bar upon occurrence of a fire.
In addition, in the case of an apparatus for measuring elongation of a test sample, since the apparatus is not configured to test without affection by the heat under the high temperature condition, when the apparatus for testing a tensile strength is under the high temperature condition, the apparatus may be affected by the heat to be damaged or make accurate measurement difficult.